Project Summary The peptide hormone relaxin has traditionally been linked to the maternal adaptation of the cardiovascular system during the first trimester of pregnancy. By promoting nitric oxide (NO) formation through different molecular signaling events, relaxin has been proposed as a pleiotropic and cardioprotective hormone in the setting of many cardiovascular diseases. In fact, pre-clinical studies were able to demonstrate that relaxin promotes vasodilatation and angiogenesis; ameliorates ischemia/reperfusion (I/R) injury and regulates extracellular matrix turnover and remodeling following acute myocardial infarction (AMI). In the RELAX-AHF phase 3 clinical trial, serelaxin (recombinant human relaxin) was shown to be safe and it exerted survival benefits in acute heart failure (HF) patients. The relaxin receptor 1 (RXFP1) is a G-coupled cognate ligand receptor for relaxin and its expression is not only found in a wide range of reproductive tissues, but also in non- reproductive tissues including the heart. The hormone relaxin, after coupling with its cognate receptor RXFP1, activates several G-coupled proteins to promote production of cyclic adenosine mono-phosphate (cAMP), phosphorylation of mitogen-activated protein kinases and activation of the NO pathway. Several studies in adult animals have alluded to an infarct-sparing benefit of recombinant relaxin therapy, coupled with remarkable decline in inflammation and indices of adverse remodeling post MI. Recent work has also implicated beneficial effects of relaxin in reversing cardiac fibrosis and related dysfuction as well as large artery remodeling coupled with improved arterial compliance in senescent spontaneously hypertensive rats. Studies in high-fat-fed mice showed that relaxin reverses insulin resistance and its consequent vascular dysfunction. We will test the following hypotheses: Aim 1: To investigate the impact of gain-of-function and loss-of- function of RXFP1 in aging diabetic heart following I/R injury and the role of ML290 in preserving mitochondrial function and attenuating cell death post MI. Aim 2: To determine the anti-inflammatory effect of RXFP1 signaling through suppression of NLRP3-inflammasome. These studies will be the first to demonstrate that the protective effects of RXFP1 signaling against ischemic cardiomyopathy occur through attenuation of inflammasome-mediated adverse signaling and remodeling. This is especially novel and the results will have a tremendous impact on further endorsing ralxin as a potent cardioprotectant.